1. Field of the Invention
This invention relates to an improved remote control system for a combined ceiling fan and light fixture and, more particularly, to a system of this type using a radio frequency link, microprocessor control, and a number of special features.
2. Description of the Prior Art
Ceiling fans are often combined with light fixtures, and it is desirable to provide remote control means for controlling fan speed and direction as well as light intensity. One such remote control system is shown in U.S. Pat. No. 4,719,446, issued Jan. 12, 1988 to Edward F. Hart. This system uses existing house wiring to couple control signals from a wall mounted control unit to control the speed of the fan and the intensity of the light. However, systems of this character require access to an AC line by replacing a wall switch and are subject to line noise. Such systems are difficult to operate in that fan and light operations are sometimes confused. Moreover, the light energization and intensity level and fan control bits for controlling the energization, speed and direction of the fan.
The combined ceiling fan and light fixture (hereinafter the "ceiling unit") includes a radio receiver which receives the transmitted digital signal and provides a data signal corresponding to the digital signal to a second microprocessor. The second microprocessor controls light energization and intensity level, in accordance with the light fixture control bits and fan energization, direction and speed in accordance with the fan control bits.
It is sometimes convenient to employ two control units at different locations in a room to control the same ceiling unit or units. Because the control units operate autonomously, there is a problem when the fan units receive conflicting commands at random times. According to the invention, this problem is solved by providing a special bit (an "A/B" bit) in the control code stream to identify the control unit transmitting the signal and a "manual/automatic" bit in the control code stream to identify whether a command is a manual command input through the manual entry means or an automatic command derived from temperature sensor readings. The second microprocessor then controls the ceiling unit to respond to the control unit which was last operated manually.
For complete recovery from power failures and to boost the accuracy of the system to simulate a closed loop controller's accuracy, the control unit transmits an update every hour, if no functions are requested (fan, light and features "off"). When any function or component is "on", updates are transmitted every ten minutes. Any time a transmission is called for by a temperature change or by manual operation, the update timer within the second microprocessor is reset.
In order to provide draft-free recirculation of heated air in winter, a "winter" mode is provided. In this mode, the second microprocessor controls fan operation to provide upward airflow at low speed. Every five minutes, the fan speed is increased for ten seconds before returning to the low speed. This is just enough to break up stratification, while the low speed keeps the air moving gently so as not to create a draft.
For controlling fan speed in response to temperature changes in the room as sensed by the temperature sensor, an "auto-speed" mode is provided. The control unit tests room temperature every thirty seconds. Every two minutes, a temperature determination is updated with the average of the last three readings. This determined temperature is compared to a base temperature and a target speed is computed from the temperature difference. If the fan speed is not then at the target speed, a command is transmitted to change fan speed to the target speed.
The system of the invention also can operate in "security", "power saver" and "test" modes.
In the ceiling unit, the second microprocessor controls triacs which determine fan direction and speed. As mentioned above, it is the conventional practice to trigger the triacs continuously. The power consumption of continuous triggering is substantially reduced, according to the invention, by triggering the triacs just before the time of zero crossing of the AC power supply through a short period ending just after the time of zero crossing to make sure the triac is solidly on throughout the period of commutating effects. The triggering current is then removed until just before the next zero crossing.